Method for manufacturing magnetic core

ABSTRACT

The invention provides an apparatus (with a corresponding method) for manufacturing a magnetic wound core of a toroidal transformer. The apparatus in accordance with a preferred embodiment of the invention comprises a control device for controlling the apparatus based on parameters of the core material and the wound core, a supplying device for providing the core material ribbon, a grinding device for grinding the lateral edges of the core material ribbon under the control of the control device, and a winding device for receiving and winding the core material ribbon into the wound core. The apparatus according to a further embodiment of the invention further comprises a calibration device for keeping the core material leaving from the supplying device horizontally and centered, a counting device for measuring the length of the core material passing therethrough, a punch device for cutting off the core material ribbon under the control of the control device, a selecting device for directing the core material ribbon for disposal under the control of the control device, and an unloading device for taking the wound core out of the winding device.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates generally to an apparatus and method formanufacturing a magnetic core of a toroidal transformer and, moreparticularly, to on apparatus and method for manufacturing a woundmagnetic core of a toroid transformer with an R-angle.

2. Description of the Related Art

A transformer is an electrical device used to provide a low-voltagepower supply from a high-voltage alternating-current (AC) power source,or a high-voltage supply from a low-voltage AC power source. In its mostbasic form, a transformer consists of a primary coil connected to an ACvoltage source for receiving energy therefrom, a secondary coilconnected to a load for receiving energy from the primary coil andtransmitting to the load, and a core supporting the coils for providinga path for the magnetic lines of flux. The magnetic field (flux) buildsup (expands) and collapses (contracts) about the primary coil. Theexpanding and contracting magnetic field around the primary coil cutsthe secondary coil and induces an alternating voltage into the coil.This voltage causes alternating current to flow through the load. Thevoltage may be stepped up or down depending on the design of the primaryand secondary coils.

Transformers are frequently classified on the basis of their uses andpurposes, whereas the detailed constructions of the transformers dependon the intended application. Power transformers are generally used totransmit power at a constant frequency. Audio transformers are designedto operate over a wide range of frequencies with a nearly flat response,i.e., a nearly constant ratio of input to output voltage. Radiofrequency (RF) transformers are designed to operate efficiently within anarrow range of high frequencies.

Transformers often include silicon steel cores to channel the magneticfield. Such cores keep the magnetic field more concentrated around thecoils so that the transformer is more efficient. The cores also keep themagnetic field from being unnecessarily wasted in adjacent pieces ofmetal. A commonly available transformer core is the toroid core. Atoroid transformer is made by placing coils around a core having aclosed annular form. The toroid core can be made from magnetic metalalloy by casting, by lamination from magnetic metal alloy sheets, or bywinding from a continuous magnetic metal alloy ribbon.

According to a method and apparatus in the art for manufacturing a woundtoroidal transformer core, a continuous ribbon of annealed amorphousmagnetic core material is removed from a supply spool and wound into anannular cavity defined by a rotating bobbin within a partially assembledtoroidal transformer. Efforts are accordingly made to prevent thevarnish coating on the coils from being damaged during the subsequentcoil winding process. Typically, a lathe machine will be utilized togrind the radial corners of the wound core into an R-angle such that thecoils are wound more tightly and uniformly onto the wound cores, asopposed to those without an R-angle.

However, since the inner and outer diameters of the wound toroidal coresare generally different, a set of clamping devices for accommodatingdifferent sizes of the wound cores are needed in advance for the lathemachine for securely clamping the wound core. Such disadvantageouslymakes the manufacturing process unduly burden some significantlyincrease the cost of the manufacturing equipments. In addition, smallparticles, which come off the wound core during the lathing process andenter into spaces between layers of the wound core material, becomeindependent conductors that adversely affect the magnetic lines of fluxtherein. Moreover, iron loss is significantly increased due to damage onthe insulating layers of the radial corners of the wound cores.

There is thus a general need in the art for an optimally designed andimplemented wound magnetic core for a toroid transformer thatadvantageously overcomes at least the aforementioned shortcomings in theart.

SUMMARY OF THE INVENTION

In view of the above problems in the art, a primary object of theinvention is to provide an apparatus (with a corresponding method) formanufacturing a magnetic core with an R-angle, which advantageouslyreduces the copper loss, saves the coil material and increases the yieldof the toroidal transformers including a wound toroid core thus formed.

The invention accordingly provides an apparatus for manufacturing amagnetic wound core with an R-angle, comprising a control device forcontrolling the apparatus based on parameters of the core material andthe wound core, a supplying device for providing the core materialribbon, a grinding device for grinding the lateral edges of the corematerial ribbon under the control of the control device, and a windingdevice for receiving and winding the core material ribbon into the woundcore.

In an embodiment of the invention, the apparatus for manufacturing amagnetic wound core with an R-angle further comprises a calibrationdevice for keeping the core material leaving from the supply devicehorizontally and centered, a counting device for measuring the length ofthe core material passing therethrough, a punch device for cutting thecore material ribbon into a predetermined length, a selecting device fordirecting the core material of a predetermined length for disposal ifthe length of the core material ribbon is not the predetermined lengthand a unloading device for taking the wound core out of the windingdevice.

In accordance with a further embodiment of the invention, a method isadvantageously provided for manufacturing a magnetic wound core havingan R-angle from a core material ribbon. The method according to thisparticular embodiment comprises the steps of cutting the core materialribbon into a predetermined length, forming the core material ribbonhaving lateral edges into a spread-out shape (such as a generallytrapezoidal shape), grinding the lateral edges of the core materialribbon, and winding the core material ribbon into the core wound. dr

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will become more apparent from the detailed descriptiongiven herein and below when read in conjunction with the accompanyingdrawings (not necessarily drawn to scale), which are given by means ofillustration only (and thus are not exhaustive) of the variousembodiments of the invention, in which:

FIG. 1 is a schematic plan view illustrating an exemplary apparatus formanufacturing a magnetic core with an R-angle in accordance with apreferred embodiment of the invention;

FIG. 2 is an exploded perspective view of the apparatus exemplarilyshown in FIG. 1

FIG. 3 is a schematic view illustrating an exemplary calibrating devicein accordance with an embodiment of the invention;

FIG. 4 is a schematic view illustrating an exemplary counting device inaccordance with an embodiment of the invention;

FIG. 5 is a schematic view illustrating an exemplary grinding device inaccordance with an embodiment of the invention;

FIG. 6 is a schematic view illustrating an exemplary receiving/feedingdevice for the grinding device shown in FIG. 5;

FIG. 7 is a schematic view illustrating an exemplary punching device inaccordance with an embodiment of the invention;

FIG. 8 a schematic view generally illustrating an exemplary operation ofthe punching device shown in FIG. 7;

FIG. 9 is a schematic view illustrating an exemplary winding device inaccordance with an embodiment of the invention;

FIG. 10 is an exploded perspective view illustrating the structure of anexemplary clamping device in accordance with an embodiment of theinvention;

FIG. 10A and FIG. 10B are schematic views illustrating an exemplaryoperation of the clamping device shown in FIG. 10;

FIG. 11 is a schematic view illustrating an exemplary unloading devicein accordance with an embodiment of the invention;

FIG. 12 is a schematic view illustrating an exemplary selecting devicein accordance with an embodiment of the invention; and

FIG. 12A and FIG. 12B are schematic views illustrating an exemplaryoperation of the selecting device shown in FIG. 12.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

In accordance with the invention, an exemplary shape of the corematerial forming a wound core having an R-angle as it spreads out is anelongated ribbon having a generally trapezoid shape, in which the widthof the ribbon at the inner side of the wound core is smaller than thewidth at the outer side thereof. The invention utilizes such a principleto provide the core material ribbon with an appropriate shape forfurther winding so as to readily form a wound core with an R-angle,rather than forming a wound core and then further lathing the radialcorners of the wound core to form an R-angle.

The apparatus for manufacturing a magnetic wound core with an R-angle inaccordance with a preferred embodiment of the invention comprises acontrol device for controlling the apparatus based on parameters of thecore material and the wound core, a supplying device for providing thecore material ribbon, a grinding device for grinding the lateral edgesof the core material ribbon under the control of the control device, anda winding device for receiving and winding the core material ribbon intothe wound core.

With reference to FIG. 1 and FIG. 2, an apparatus 10 for manufacturing awound core 200 of a toroidal transformer in accordance with a preferredembodiment of the invention is shown. The apparatus 10 comprises asupply device 20 having a rotatable supply spool 24, a calibrationdevice 30, a counting device 40, a grinding device 50, a punching device60, a selecting device 70, a winding device 80, an unloading device 90and a control device 100. A reel of core material 22, such as siliconsteel, is wrapped at the supply spool 24. The core material 22 leavingfrom the supply spool 24 enters into the calibration device 30, wherethe core material 22 is kept to be horizontal and centered along itsaxial center so as to ensure the alignment thereof for the subsequentprocesses, such as grinding and wrapping. The core material 22 leavingfrom the calibration device 30 further passes through the countingdevice 40, where the length of core material passing therethrough iscalculated. The length information is transmitted to the control device100 for determination of the dimensions of the core material based onthe input data, such as width of the core material provided from thesupply device 20, the inner and outer diameters of the final wound core,and for controlling the operations of all the devices of the apparatusaccording to the invention. The core material 22 then enters into thegrinding device 50. Based on the dimension information calculated andprovided by the control device 100, the edges of the core material 22are ground in the grinding device 50 to gradually reduce the width ofthe core material 22 so as to form an appropriate shape, such as thespread-out shape of a final wound core with an R-angle, or an elongatedtrapezoid shape. The punch device 60 receives the length informationfrom the control device 100 and accordingly cuts the core material offonce a predetermined length of core material has passed through. Thecore material ribbon further enters into the winding device 80 and iswound to form a toroidal core with an R-angle. After the wound core iscompleted, the unloading device 90 takes the wound core from the windingdevice 80 by utilizing a pair of robot arms 92. Exemplary operations ofeach device in the apparatus 10 are described herein and below infurther detail.

FIG. 3 is a schematic view that exemplarily illustrates a calibrationdevice 30 in accordance with a preferred embodiment of the invention.The calibration device 30 accordingly comprises a rough alignment device32 having a cylindrical roller 32 a and a sandglass-shaped roller 32 b,composing of two cone-shaped rollers 32 b 1 and 32 b 2, and ahorizontally disposed fine alignment device 34 having twosandglass-shaped rollers 34 a and 34 b, each of which is composed of twocone-shaped rollers, and a pair of cylindrical rollers 34 c and 34 ddisposed between the sandglass-shaped rollers 34 a and 34 b. The corematerial ribbon 22 leaving from the supply device 20 first enters intothe rough alignment device 32 with one surface of the core materialribbon in contact with the cylindrical roller 32 a and the other surfaceof the core material ribbon in contact with and facing toward thesandglass-shaped roller 32 b. The cylindrical roller 32 a primarilyserves to direct the core material ribbon 22 to the sandglass-shapedroller 32 b. At the sandglass-shaped roller 32 b, the lateral edges ofthe core material ribbon 22 are in contact with the cone-shaped rollers32 b 1 and 32 b 2, respectively. The cone-shaped rollers 32 b 1 and 32 b2 are coupled to each other so that they are rotatable in generally thesame direction at generally the same rotating speed. In this manner, thecontact positions between the lateral edges of the core material ribbonand the corresponding cone-shaped rollers 32 b 1 and 32 b 2 areadvantageously self-adjusted so as to maintain the linear speed of eachedge of the core material ribbon the same. The cone material ribbon as awhole accordingly moves to the fine alignment device 34 at a generallyconstant linear speed.

The core material ribbon further enters into the fine alignment device34. The operation and function of the sandglass-shaped rollers 34 a and34 b are similar to those described herein for sandglass-shaped rollers32 b. The cylindrical rollers 34 c and 34 d, which are disposedhorizontally and parallel to each other, serve to further ensure thecore material ribbon passing therethrough being horizontal. Through therough alignment device 32 and the fine alignment device 34, the corematerial ribbon leaving the calibration device 30 moves horizontally andat a generally constant speed. Furthermore, the axial center of the corematerial ribbon is in line with the centerline of the grinding device 50and the winding device 80. In this manner, the symmetry of the grindingand winding of the core material ribbon is ensured in subsequentprocesses, which are described in further detail herein and below.

FIG. 4 is a schematic view that exemplarily illustrates a countingdevice 40 for providing necessary information for measuring the lengthof the core material ribbon 22 passing therethrough in accordance withan embodiment of the invention. The counting device 40 accordinglycomprises a pair of cylindrical rollers 42 and 44 horizontally arrangedone above the other for the core material ribbon passing therebetween.The lower roller 42 is connected to a servomotor 46 through a belt 48.The servomotor 46 counts the number of revolutions of the lower roller42 and accordingly provides the revolution data to the control device100 for further calculation of the length of core material ribbonpassing therethrough. The upper roller 44 serves to impart a sufficientdownward force on the lower roller 42 by, e.g., biased securing blocks43, so as to keep the core material ribbon tightly moving between andthrough the upper and lower rollers 42 and 44. With the thickness of thecore material ribbon changes, the biased securing blocks 43 areaccordingly adjusted to modify the vertical position of the upper roller44 (and hence the gap between the upper and lower rollers 42 and 44)such that the downward force applied to the core material is generallykept at an appropriate and sufficient magnitude.

FIG. 5 is a schematic view that exemplarily illustrates the grindingdevice 50 in accordance with an embodiment of the invention. Thegrinding device 50 accordingly comprises a device 51 for receiving andsupplying the core material ribbon, two grinding wheels 52 and 54disposed at each side of the core material ribbon for grinding the edgesof the core material ribbon, and a servomotor 55 for moving the grindingwheels 52 and 54. The servomotor 55 controlled by the control device 100(not shown in FIG. 5) actuates two ball screws 56 (only one is shown inthe drawing), one having a right-hand thread and the other having aleft-hand thread. The grinding wheels 52 and 54 are thus movinghorizontally toward or away from each other. Cams 57 are provided forvertically moving the grinding wheels 52 and 54 such that the contactposition of each of the grinding wheels 52 and 54 and the correspondingedge of the core material ribbon 22 is reciprocated within the range ofthe grinding portion of the grinding wheels 52 and 54. In this manner,grinding portions of the grinding wheels 52 and 54 are being worn in agenerally uniform fashion so that the life of the grinding wheels isadvantageously increased. In addition, the insulating layer coated onthe surfaces of the core material ribbon will not be damaged since theedges of the core material ribbon is processed by grinding, as opposedto lathing that will adversely damage the insulating layer of the corematerial ribbon.

FIG. 6A and FIG. 6B are diagrams that respectively illustrate theperspective and exploded views of the device 51 for receiving andsupplying the core material ribbon as shown in FIG. 5. The device 51accordingly comprises a flat and parallel inlet 51 a for entrance of thecore material ribbon, a curved surface 51 b transformed from a flatconfiguration to a slightly V-shaped configuration and a slightlyV-shaped outlet 51 c. The device 51 advantageously serves to enhance thestiffness of the core material ribbon for transmission such that thecore material ribbon is prevented from drooping due to its weight.

FIG. 7 and FIG. 8 are diagrams that respectively illustrate aperspective view and an exemplary operation of the punching device 60 inaccordance with an embodiment of the invention. The punching device 60primarily comprises two pairs of cylindrical rollers (62 and 64), acylinder 66 and a cutting device 68. The cylindrical rollers 62 serve toreceive and flatten the V-shaped core material ribbon, and keep the corematerial ribbon tightly moving in conjunction with the cylinder rollers64. The cutting device 68 is driven by the cylinder 66, controlled bythe control device 100 (not shown in FIG. 7 and FIG. 8), to punch on andcut the core material ribbon off while the predetermined length of thecore material ribbon is passing therethrough.

FIG. 9 is a schematic view that exemplarily illustrates the windingdevice 80 in accordance with an embodiment of the invention. The windingdevice 80 comprises a clamping device 81, pressing device 82, weldingdevice 83, first servomotor 84 for actuating the pressing device 82, setscrew 85, spring 86, cylinder 87 and second servomotor 88 for rotatingthe clamping device 81.

The clamping device 81 serves to receive and clamp one end of the corematerial ribbon. After the end of the core material ribbon is secured inposition, the clamping device 81 starts to rotate about its axis by theactuation of the servomotor 88 for winding the core material ribbon intoa wound core. During winding, the pressing device 81 presses on the corematerial ribbon with an appropriate force to ensure that the core iswound sufficiently tight. The force exerted by the pressing device 82 onthe core material ribbon is provided by the spring 86 and the magnitudeof the force is adjustable through the set screw 85. Every time theclamping device 81 completes a full turn of rotation (i.e., 360degrees), the diameter of the partially completed wound corecorrespondingly increases by the thickness of the core material. Thepressing device 82 accordingly moves away from the wound core by adistance corresponding to the thickness of the core material ribbonunder the action of the first servomotor 84. In this manner, it isensured that the pressing device 82 presses on the core material ribbonwith a pressing force of an appropriate and sufficient magnitude. Afterthe winding is complete, the welding device 83 performs spot welding tosecure the end of the core material ribbon on the wound core so that thewound core will not spread out.

FIG. 10 is a diagram that exemplarily illustrates an explodedperspective view of the clamping device 81 in accordance with anembodiment of the invention. The clamping device 81 accordinglycomprises a guiding element 120 having three dovetail slideways 120 aconnected to a rod 121 having an enlarged end portion 121 a, sliders 122each having a complementary slot 122 a for moving along thecorresponding dovetail slideway 120 a, a flange 123, a positioningcircular ring 124 for securing the sliders 122 onto the flange 123, arod 125 having a enlarged hollow head portion 125 a for containing theenlarged end portion 121 a of the rod 121, and balls 126 for beingdisposed within throughholes 125 b provided on the head portion 125 aand for restricting the moving of the enlarged end portion 121 a.

FIG. 10A and FIG. 10B are diagrams that respectively illustratesectional views of the clamping device 81 and an exemplary operationthereof. With reference to FIG. 10A, while a pulling force is exerted onthe distal end of the rod 125 by, e.g., a spring (not shown), theguiding element 120 moves in the axial direction indicated by arrow Athrough the interaction of the balls 126, the enlarged end portion 121 aand the rod 121. While the guiding element 120 moves rightward, sincethe left portion of the guiding element 120 includes a larger dimensionthan the right portion, the sliders 122 having the slots 122 a movingrelative to the dovetail slide way 120 a of the guiding element 120 areforced to move in a radially outward direction (as indicated by arrow B)until the radial outmost portions 122 b of the sliders 122 are incontact with the positioning ring 124. The end of the core materialribbon is then inserted into the space between any two of the sliders122 where the clamping device 81 starts to rotate for winding the corematerial ribbon into a wound core.

Referring to FIG. 10B, after the winding process is complete and the endof the core material ribbon is welded onto the wound core, a cylinder(not shown) punches on the distal end of the rod 125 to apply a pushingforce over the force exerted by the spring so as to move the rod 125leftward. Such a leftward movement of the rod 125 pushes the rod 121 andhence the guiding element 120 to move leftward, so that the sliders 122move in a radially inward direction (as indicated by arrow D). Due tothe radially inward movement of the sliders 122, the sliders 122 departfrom the inner side of the wound core, where the wound core is readilydispensed away from the clamping device 122 through the robot arms 92 ofthe unloading device 90, as exemplarily illustrated in FIGS. 2 and 11 atthe actuation of the control device 100.

The apparatus 10 of the invention may further comprise a selectingdevice 110 for making certain that the each final wound core productincludes generally the same dimension. FIG. 12 is a diagram thatexemplarily illustrates the selecting device 110 in accordance with anembodiment of the invention. The selecting device 110 accordinglyincludes a cylinder 112, an actuating rod 114 and a guiding plate 116.If the length data provided by the counting device 40 indicate that thelength of the core material ribbon passing through the counting device40 matches the predetermined length for a wound core, the core materialribbon 12 will accordingly pass through the underside of the guidingplate 116 with the horizontally positioned guiding plate 166, asillustrated in FIG. 12A. However, if the length data provided bycounting device 40 indicate that the length of the core material ribbondoes not reach the predetermined length, the cylinder 112 will beactuated by the control device 100 and the actuating rod 114 is turnedto force the guiding plate 16 directing the core material ribbon ofinsufficient length for disposal to a waste bin (not shown), as shown inFIG. 12B. In this manner, it is ensured that the toroidal core is woundfrom generally the same length of the core material ribbon and thusincludes generally the same product dimensions.

In accordance with a further embodiment of the invention, a method isadvantageously provided for manufacturing a magnetic wound core havingan R-angle from a core material ribbon. The method according to thisparticular embodiment of the invention comprises the steps of cuttingthe core material ribbon into a predetermined length, forming the corematerial ribbon having lateral edges into a spread-out shape (such as agenerally trapezoidal shape), grinding the lateral edges of the corematerial ribbon, and winding the core material ribbon into the corewound. The method according to this embodiment further comprises thestep of coating insulating material onto the core material ribbon withsilicon steel.

In addition, the method according to the invention can further comprisethe steps of securing one end of the core material ribbon using aclamping device, rotating the clamping device to wind the core materialribbon into the wound core, pressing on the wound core with apredetermined force, and welding another end of the core material ribbononto the wound core. A further step can also be included in applying apredetermined pressing force on the core material ribbon. Ifappropriate, the core material ribbon can be cut off and disposed of ina waste bin.

Yet another embodiment of the method according to the invention furtherprovides the step of measuring a length of the core material ribbonpassing through a counting device. In an additional embodiment, the corematerial ribbon comprises a generally flat shape in cross-section andgenerally V-shaped configuration in cross-section.

The method according to the invention can further comprise the step ofcontrolling the apparatus according to parameters of the core materialribbon and the wound core. The parameters may include the thickness andlength of the core material ribbon, and inner and outer diameters of thewound core.

Although the invention has been described with reference to thepreferred embodiments, it will be understood that the invention is notlimited to the details described thereof. Substitutions andmodifications have been suggested in the foregoing description, andother will occur to those of ordinary skill in the art. In particular,the process steps of the method according to the invention will includemethods having substantially the same process steps as the method of theinvention to achieve substantially the same result. Therefore, all suchsubstitutions and modifications are intended to be within the scope ofthe invention as defined in the appended claims and their equivalents.

1-20. (Cancelled)
 21. A method for manufacturing a magnetic wound corehaving an R-angle from a core material ribbon, the method comprising thesteps of: cutting the core material ribbon into a predetermined length;forming the core material ribbon having lateral edges into a spread-outshape; grinding the lateral edges of the core material ribbon; andwinding the core material ribbon into the core wound.
 22. The method ofclaim 21 wherein the spread-out shape is a generally trapezoidal shape.23. The method of claim 21 further comprising the step of coatinginsulating material onto the core material ribbon with silicon steel.24. The method of claim 21 further comprising the steps of: securing oneend of the core material ribbon using a clamping device; rotating theclamping device to wind the core material ribbon into the wound core;pressing on the wound core with a predetermined force; and weldinganother end of the core material ribbon onto the wound core.
 25. Themethod of claim 21 further comprising the step of applying apredetermined pressing force on the core material ribbon.
 26. The methodof claim 21 further comprising the step of measuring a length of thecore material ribbon passing through a counting device.
 27. The methodof claim 21 further comprising the steps of: cutting off the corematerial ribbon; and disposing of the core material ribbon.
 28. Themethod of claim 21 wherein the core material ribbon comprises agenerally flat shape in cross-section and generally V-shapedconfiguration in cross-section.
 29. The method of claim 21 furthercomprising the step of controlling the apparatus according to parametersof the core material ribbon and the wound core.
 30. The method of claim28 wherein the parameters comprise thickness and length of the corematerial ribbon, and inner and outer diameters if the wound core.